1. Field of the Invention:
The invention relates to a method and apparatus for effecting the plugging of a subterranean well conduit, and particularly to effecting the plugging subsequent to the perforation of the well casing or similar well conduit and coincident with the removal of the discharged perforating gun from the well.
2. History of the Prior Art:
The utilization of tubing mounted perforating guns has shown a marked increase in recent years. The tubing carried perforating gun offers flexibility in the methods of discharging the gun, permitting discharge by a dropped detonating bar, or by fluid pressure introduced through the tubing on which the gun is carried. More importantly, the mounting of the perforating gun on a tubing string, which, in some instances, could constitute the production conduit, permits an immediate flow of production fluid from the perforated zone through the simple expedient of providing a ported nipple in the tubing string immediately above the perforating gun. Alternatively, a ported sleeve valve which is opened by the fluid pressures generated in the well bore subsequent to discharge of the perforating gun may be employed as described in co-pending application, Ser. No. 551,764, filed Nov. 14, 1983 and assigned to the Assignee of this application. Such arrangement permits an immediate flow of production fluid from the perforated production formation and is very desirable in that it effects the removal of perforation debris from the formation and, if the particular formation does not require additional treatment, immediate production from the formation can be initiated.
The older method of perforating wells was to effect the perforation by a wireline carried gun and immediately introduce a kill fluid to keep the well under control while the perforating gun was removed and production conduit installed. The introduction of a kill fluid into the perforated production zone is always deleterious to the formation and many efforts have been made in the past to avoid such introduction. When, however, it is necessary to interrupt the flow of production fluid in the newly formed perforations for any reason, then the well operator generally had to resort to introduction of a kill fluid.
It would therefore be obviously desirable to permit the plugging a well subsequent to the perforation operation to permit the perforating gun to be removed and the introduction of well completion equipment without relying upon the use of a kill fluid to maintain the well under control.